Optical Nanocavity Boosts Light Absorption

An optical nanocavity that boosts light absorption in ultrathin semiconductors could potentially improve solar cells, cameras and even the development of hydrogen fuel. The technology is currently in development by a team from the University at Buffalo (UB), Fudan University and Northeastern University of China.

International researchers are developing an optical nanocavity that boosts light absorption in ultrathin semiconductors. Courtesy of University at Buffalo.

“The nanocavity has many potential applications,” said Haomin Song, a Ph.D. candidate in electrical engineering at UB. “It could help boost the amount of light that solar cells are able to harvest; it could be implanted on camera sensors, such as those used for security purposes that require a high-speed response.”

Harvard University researchers have had varying degrees of success in similar research recently by combining thin films of germanium on a gold surface.

However, Suhua Jiang, associate professor of materials science at Fudan University and a member of the international team, noted that gold is a very expensive material to use. His team instead used less expensive alternatives: aluminum, aluminum oxide and germanium.

The team demonstrated light passing through the germanium — 1.5 to 3 nm thick — and circulating in a closed path through the aluminum oxide and aluminum. The light absorption rate peaked at 90 percent, with germanium absorbing about 80 percent and aluminum absorbing the rest.

Song said that these rates are ideal because the bulk of the light stays within the semiconducting material.

“We’re just scratching the surface, but the preliminary work that we’ve done is very promising,” said Dr. Qiaoqiang Gan, an assistant professor of electrical engineering at UB. “This advancement could lead to… areas that will benefit humankind.”

While more research is needed — specifically as it relates to how the semiconductor would turn light into power as opposed to heat — the team will also collaborate with other colleagues to develop ultrathin energy-harvesting devices as well as to study its effects on the photocatalytic splitting of water using energy from light, which could subsequently aid in the development of hydrogen fuel.

The work is supported by the National Science Foundation and is published in Advanced Materials. (doi: 10.1002/adma.201305793)

For more information, visit: www.buffalo.edu